In recent years, due to digitalization of television broadcasting, various needs or services which have been beyond imagination in general broadcasting are beginning to emerge. As to a channel which only broadcasts movie programs, for example, a technology of copy guard is important to protect a copyright so as not to allow an unlimited copy on the receiver. Recently, therefore, it was proposed to multiplex information such as copy guard into a digital broadcast wave as additional information and to carry the copy guard in the wave so as to allow the receiver to utilize the same. Such additional information is classified according to a standard such as CGMS (IEC1880) and WSS (ETS300, 294). As to methods how to utilize the additional information, various methods are now under consideration.
The digital broadcast wave is inputted to the receiver in the form of a bit stream. Therefore, when the receiver is going to utilize the aforementioned additional information, the receiver first recognizes the additional information multiplexed into the digital broadcast wave, and separates the same. Thereafter the receiver generates an analog video signal from the digital broadcast wave, and then inserts the separated additional information into a retrace interval of the analog video signal to output. By performing such processing, it becomes possible to utilize the additional information in various types of peripheral equipment (for example, a video tape recorder) on the receiver. The aforementioned series of signal processing can be executed by a television signal processor illustrated below.
FIG. 8 shows a block diagram which is an exemplary conventional television signal processor 100. The television signal processor shown in FIG. 8 is formed by a decoding part 101, a CPU interface (hereinafter, referred to as CPUI/F) 103, a RAM interface (hereinafter, referred to as RAMI/F) 105, video data reading part 106, OSD data reading part 107, a horizontal/vertical synchronous pulse generating part 108, a video data line buffer 109, an OSD data line buffer 110, combining part A 111, a CGMS timing generating part 112, a CGMS data buffer 113 and a combining part B 114.
The decoding part 101 generates video data by processing an inputted video stream, and then outputs the same to a work RAM 102 through the RAMI/F 105. The work RAM 102 stores the video data. Referring to FIG. 8, a CPU 104 shown outside the conventional television signal processor generates OSD data. Herein, OSD (On Screen Display) stands for a channel, a receiving mode, a volume, characters of text broadcasting and the like displayed on a currently operating television screen. The OSD is generated on the basis of the OSD data generated by the CPU 104. The OSD data generated by the CPU 104 is inputted to the work RAM 102 through the CPUI/F 103 and the RAMI/F 105. The work RAM 102 stores the inputted OSD data.
The video data reading part 106 reads the video data stored in the work RAM 102 at prescribed timing. The read timing at this time is defined on the basis of a read timing signal for the work RAM 102 inputted from the CPU 104 through the CPUI/F 103 and the RAMI/F 105, and a vertical pulse and a horizontal pulse generated by the horizontal/vertical synchronous pulse generating part 108. The video data read from the work RAM 102 is temporarily stored in the video data line buffer 109. The OSD data reading part 107 reads the OSD data from the work RAM 102 in a manner similar to the above. The read OSD data is temporarily stored in the OSD data line buffer 110.
The combining part A 111 combines the video data inputted from the video data line buffer 109 and the OSD data inputted from the OSD data line buffer 110. Additional information (here assumed to be CGMS) separated from the broadcast wave inputted from the CPU 104 through the CPUI/F 103 is temporarily stored in the CGMS data buffer 113. The CGMS timing generating part 112 generates a synthetic timing signal on the basis of the horizontal synchronous pulse and the vertical synchronous pulse generated by the horizontal/vertical synchronous pulse generating part 108. In the combining part 114, the CGMS data is synchronized with the synthetic timing signal generated by the CGMS timing generating part 112, and is combined with the video data with which the OSD data was combined.
As described above, for the conventional television signal processor, the second combining part 114 further combining the additional information such as copy guard (here CGMS) into the video data with which the OSD data has been combined was required in addition to the first combining part 111 combining the OSD data to the video data. This results in a complicated structure and a higher cost.
Further, the conventional television signal processor has been aimed at receiving only a digital broadcast wave of a predetermined standard. Therefore, the synthetic timing for the video data, the OSD data and the additional information is fixedly set. Consequently, if the standard of the received digital broadcast wave is different from the previously planned standard, the conventional television signal processor cannot recognize such change, and accordingly cannot combine the video data, the OSD data and the additional information at proper timing.
Therefore, an object of the present invention is to provide a television signal processor which can, even if the standard of a received broadcast wave changes, flexibly cope with such change with a simpler structure and a lower cost.